• 한국공작기계학회논문집
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• 제12권5호
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• pp.53-58
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• 2003

Wear debris can be collected from the lubricants of operating machinery and its morphology is directly related to the fiction condition of the interacting materials from which the wear particles originated in lubricated machinery. But in order to predict and estimate working conditions, it is need to analyze the shape characteristics of wear debris and to identify. Therefore, if the shape characteristics of wear debris is identified by computer image analysis and the neural network, The four parameter (50% volumetric diameter, aspect, roundness and reflectivity) of wear debris are used as inputs to the network and learned the friction. It is shown that identification results depend on the ranges of these shape parameters learned. The three kinds of the wear debris had a different pattern characteristic and recognized the friction condition and materials very well by neural network. We resented how the neural network recognize wear debris on driving condition.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권11호
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• pp.735-741
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• 1999

The monitoring and assessment on the insulation condition of generator stator windings have been an important task of utility companies. The interest for the assessment of insulation condition has been increasing due to the need to keep old generating equipment reliable in order to extend the equipment life and to increase the generating capacity. Even though many developments and research activities for the condition assessment of generator insulation have been performed for decades, the assessment criterion in order to consistently predict the actual insulation condition is still in question. In this paper, the correlation between the parameters and the insulation condition is analyzed through the various non-destructive diagnostic tests in order to establish the assessment criterion on insulation deterioration of generator stator windings. By analyzing the correlation, PDI(Partial Discharge Index) as a novel parameter for the assessment criterion on insulation diagnosis of stator winding is proposed and verified.

• 한국전산구조공학회논문집
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• 제26권6호
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• pp.447-454
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• 2013

모델기반 고장 진단법은 풍력발전기의 상태감지 시스템(Condition monitoring system)에 적용을 목적으로 변동 하중조건하에서 작동하는 기어박스내의 기어의 균열을 진단하기 위해 제시하였다. 두 개의 평기어(Spur gear)로 구성된 간단한 테스트 베드가 위의 접근방법을 검증하기 위해 구축되었고, 기어의 균열은 기어의 뿌리부분에 균열을 인가하여 묘사하였다. 축의 회전속도에 독립적인 타코미터를 기반으로 한 오더분석(Order analysis)을 균열크기 진단에 적용하였고, 테스트 베드의 작동을 시뮬레이션하기 위해 집중변수 모델(Lumped parameter dynamic model)이 사용되었다. 모델에서 균열과 밀접히 관련된 변수는 측정된 신호와 시뮬레이션된 신호 간의 차이를 최소화하는 최적화 기법으로 역추정하였다. 제시한 방법의 유효성을 보이기 위해, 미리 정의된 모델 변수로부터 생성된 시뮬레이션 신호를 테스트-베드로부터 측정된 신호로 가정하고, 제시한 방법을 사용하여 변수를 역추정하였다. 결과는 실제 값과 일치하였고, 이를 통해 알고리즘이 제대로 작동함을 알 수 있었다. 다음 연구에서는 실제 테스트 베드의 실제균열에 적용하고자 한다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1509-1518
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• 2011

Shield TBM tunneling method has been getting the spotlight for urban tunneling. It can be minimized the civil complaint during construction and possible safe tunneling. But the settlement has occurred inevitably due to characteristics of shield TBM equipment. For this reason, the civil complaint can occur in urban areas when tunnel with shallow depth passes through neighboring building or residential area. In this study, the occurrence factors of settlement according to shield TBM tunneling and the tendency of ground settlement by strata condition had analyzed. It is suggested that the practical settlement estimation method and minimizing method of ground settlement under simultaneous backfill grouting condition through measurement results and back analysis data using gap parameter.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1145-1150
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• 2005

The aim of this paper is to investigate the effect of surface texturing on metal surface and to understand the potential of friction reduction through micro-scale dimple to fabricate by photolithography on pin-on-disk test using flat-on-flat contact geometry. It was verify that the friction property with respect to the same pitch has been influence on the size of dimple under lubricated sliding contact. Also, we can recognize from Stribeck curve that the friction property has a connection with the size of dimple. It can explain a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. The friction property has been an effect on the size of surface texture on reduction friction, not only because the density of dimple, but also because the ratio of diameter/pitch. This ratio of approximately 0.5 is recommend under the tested friction condition. It suggested that the ratio of d/p is an important parameter for surface texture design.

• 소음진동
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• 제11권2호
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• pp.329-335
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• 2001

The analytical model of the ground wave can be used for the prediction of the noise level from a source above a plain and homogeneous ground surface with no obstacles nearby. Sound propagation along the surface of the ground can be affected by the roughness of the ground surface and the direction of the wind. The effects of the ground surface and the wind can be formulated in terms of the ground coefficient and the noise source parameter. Upward and downward conditions can also be addressed by considering the direction of the wind. The ground coefficient and the noise source parameter are estimated using the measured noise levels of two points under particular environmental condition, and the noise levels of arbitrary points under the same environmental condition can be estimated. The proposed method can be utilized to estimate the noise level of specific noise environment and its validity was confirmed with the results of actual field measurement.

• 대한수학회보
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• 제51권2호
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• pp.409-421
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• 2014

This paper deals with the superlinear elliptic problem without Ambrosetti and Rabinowitz type growth condition of the form: $$\{-div\((1+\frac{|{\nabla}u|^{p(x)}}{\sqrt{1+|{\nabla}u|^{2p(x)}}}})|{\nabla}u|^{p(x)-2}{\nabla}u\)={\lambda}f(x,u)\;a.e.\;in\;{\Omega}\\u=0,\;on\;{\partial}{\Omega}$$ where ${\Omega}{\subset}R^N$ is a bounded domain with smooth boundary ${\partial}{\Omega}$, ${\lambda}$ > 0 is a parameter. The purpose of this paper is to obtain the existence results of nontrivial solutions for every parameter ${\lambda}$. Firstly, by using the mountain pass theorem a nontrivial solution is constructed for almost every parameter ${\lambda}$ > 0. Then we consider the continuation of the solutions. Our results are a generalization of that of Manuela Rodrigues.

• 통합자연과학논문집
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• 제13권3호
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• pp.92-96
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• 2020

Taguchi's robust parameter design is an approach to reduce the performance variation of quality characteristics in products and processes. In robust design, the signal-to-noise ratio (SN ratio) was used to find the optimum condition to minimize the variation of quality characteristics as much as possible and bring the average of quality characteristics closer to the target value. In this paper, we propose a simultaneous optimization method based on a linear model of the SN ratio as a method to find the optimal condition of the control factor in case of multi-characteristics. In addition, the proposed method and the existing method were compared and studied by taking actual cases.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.506-509
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• 2008

Mathematical models have been developed to calculate hydrodynamic characteristics of perforated-wall structures. Most of the models separate the fluid regions into front and back of the wall, assume the solution in each region, and calculate the solution by using the matching condition at the wall. The matching condition involves the permeability parameter, which can be calculated by the methods proposed by Mei et al. or Sollitt and Cross. In this study, we compare these two methods. The former is advantageous because all the related variables are known, but it gives wrong result in the limit of long waves, i.e. zero transmission and perfect reflection of very long waves. In deep water, the latter predicts smaller transmission and larger reflection than the former, and vice versa in shallow water. In the latter method, the friction coefficient decreases as the wall thickness or the porosity of the wall increases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.262-267
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• 2001

In this study, the Reliability of degraded steam turbine blade was evaluated using the limited fatigue data. The statistical estimation of limited fatigue data implies that some unknown uncertainties which may be involved in fatigue reliability analysis. Therefore, an appropriate distribution in the fatigue strength was determined by the characteristic distribution - linear correlation coefficient, fatigue physics, error parameter. 3-parameter Weibull distribution is the most appropriate distribution to assume for infinite region. The load applied on the blade is mainly tensile. The maximum Von-Mises stress is 219.4 MPa at the steady state service condition. The failure probability($F_p$) derived from the strength-stress interference model using Monte carlo simulation under variable service condition is 0.25% at the 99.99% confidence level.